Create a link list Add some nodes to it search and delete no

Create a link list. Add some nodes to it, search and delete nodes from it.

Solution

#include <iostream>
#include <cstddef>

using std::cout;
using std::endl;

/*
A linked list is a list constructed using pointers. It is not fixed in
size and could grow and shrink while the program is running.

A typical defination of list nodes contains at least two parts, both the
content or date of each element and the pointer to the next element,
which is shown in the figure below.

+---------+
| Data | -----> holds the data of this element in the list.
+---------+
| pointer | -----> is a pointer to the next element in the list.
+---------+

***Attention***:
The pointer holds the address of the next element, not the address of the
data in the next element, even though they are the same in value sometimes.
And It should be set to NULL while acting as the last node of the list.


Implementation of the single linked list:
+---------+ --->+---------+ --->+---------+
| Data | | | Data | | | Data |
+---------+ | +---------+ | +---------+
| pointer |----- | pointer |----- | pointer |
+---------+ +---------+ +---------+
*/

/* definition of the list node class */
class Node
{
friend class LinkedList;
private:
int _value; /* data, can be any data type, but use integer for easiness */
Node *_pNext; /* pointer to the next node */
  
public:
/* Constructors with No Arguments */
Node(void)
: _pNext(NULL)
{ }
  
/* Constructors with a given value */
Node(int val)
: _value(val), _pNext(NULL)
{ }
  
/* Constructors with a given value and a link of the next node */
Node(int val, Node* next)
: _value(val), _pNext(next)
{}
  
/* Getters */
int getValue(void)
{ return _value; }
  
Node* getNext(void)
{ return _pNext; }
};

/* definition of the linked list class */
class LinkedList
{
private:
/* pointer of head node */
Node *_pHead;
/* pointer of tail node */
Node *_pTail;
  
public:
/* Constructors with No Arguments */
LinkedList(void);
/* Constructors with a given value of a list node */
LinkedList(int val);
/* Destructor */
~LinkedList(void);
  
/* Function to add a node at the head of a linked list */
void headInsert(int val);
/* Function to add a node in the middle of a linked list */
void insertAfter(Node* afterMe, int val);
/* Function to append a node to the end of a linked list */
void tailAppend(int val);
  
/* Function to get the node in the specific position */
Node* getNode(int pos);
  
/* Traversing the list and printing the value of each node */
void traverse_and_print();
};

LinkedList::LinkedList()
{
/* Initialize the head and tail node */
_pHead = _pTail = NULL;
}

LinkedList::LinkedList(int val)
{
/* Create a new node, acting as both the head and tail node */
_pHead = new Node(val);
_pTail = _pHead;
}

LinkedList::~LinkedList()
{
/*
* Leave it empty temporarily.
* It will be described in detail in the example \"How to delete a linkedlist\".
*/
}

void LinkedList::headInsert(int val)
{
/* The list is empty? */
if (_pHead == NULL) {
/* the same to create a new list with a given value */
_pTail = _pHead = new Node(val);
}
else
{
/* Create a new node and insert it before the head node */
Node *node = new Node(val);
node->_pNext = _pHead;
/* Update the head node */
_pHead = node;
}
}

void LinkedList::insertAfter(Node* afterMe, int val)
{
if(afterMe != NULL)
{
/* The image of inserting a node like the figures below
before inserting:
+---------+ --->---------+ --->+---------+
| afterMe | | | Node(a) | | | others |
+---------+ | +---------+ | +---------+
| next |----- | next |----- | NULL |
+---------+ +---------+ +---------+
after inserting:
(1)
+---------+ --->+---------+ --->+---------+ --->+---------+
| afterMe | (3)| | New Node| (2)| | Node(a) | | | others |
+---------+ | +---------+ | +---------+ | +---------+
| next |----- | next |----- | next |----- | NULL |
+---------+ +---------+ +---------+ +---------+

* There are three steps to insert a node into a list
* Step(1): shown as (1) in the figure above
Create a new node to be inserted
* Step(2):
Make the \"next\" pointer of the New Node point to the Node(a)
* Step(3):
Make the \"next\" pointer of the afterMe node point to the New Node
*/
afterMe->_pNext = new Node(val, afterMe->_pNext);
}
}

void LinkedList::tailAppend(int val)
{
/* The list is empty? */
if (_pHead == NULL) {
/* the same to create a new list with a given value */
_pTail = _pHead = new Node(val);
}
else
{
/* Append the new node to the tail */
_pTail->_pNext = new Node(val);
/* Update the tail pointer */
_pTail = _pTail->_pNext;
}
}

Node* LinkedList::getNode(int pos)
{
Node* p = _pHead;
/* Counter */
while (pos--) {
if (p != NULL)
p = p->_pNext;
else
return NULL;
}
return p;
}

void LinkedList::traverse_and_print()
{
Node *p = _pHead;
  
/* The list is empty? */
if (_pHead == NULL) {
cout << \"The list is empty\" << endl;
return;
}
  
cout << \"LinkedList: \";
/* A basic way of traversing a linked list */
while (p != NULL) { /* while there are some more nodes left */
/* output the value */
cout << p->_value << \" \";
/* The pointer moves along to the next one */
p = p->_pNext;
}
cout << endl;
}

int main(int argc, const char * argv[])
{
/* Create a list with only one node */
LinkedList list(1);
cout << \"Create a list with only one node\" << endl;
/* output the result */
list.traverse_and_print();
  
/* Add a node with value 2 at the head of the list */
list.headInsert(2);
cout << \"Add a node with value 2 at the head of the list\" << endl;
/* output the result */
list.traverse_and_print();
  
/* Append a node with value 3 to the end of the list */
list.tailAppend(3);
cout << \"Append a node with value 3 to the end of the list\" << endl;
/* output the result */
list.traverse_and_print();
  
/* Insert a node with value 4 after the first node of the list */
list.insertAfter(list.getNode(0), 4);
cout << \"Insert a node with value 4 after the first node of the list\" << endl;
/* output the result */
list.traverse_and_print();
  
return 0;
}